Lactate Threshold Marathon Pace: Which Threshold?
Lactate threshold marathon pace depends on which threshold you mean. One fictional step test gives marathon projections from 2:46 to 3:22.
Marathon pace is not run at "the" lactate threshold. For trained runners it typically sits between the first threshold (LT1, where lactate first rises above baseline) and the second (LT2, the highest intensity where lactate production and clearance still balance), usually much closer to LT1. So the useful question behind "lactate threshold marathon pace" is which threshold your number refers to, because on one step test the candidates can translate into marathon times more than 30 minutes apart.
Two thresholds, and why the marathon falls between them
Faude, Kindermann and Meyer's 2009 review in Sports Medicine found 25 different lactate threshold concepts and sorted them into three groups: fixed blood lactate values, the first rise above baseline, and concepts that target the maximal lactate steady state (MLSS) or a sharp bend in the lactate curve. Their framework rests on two breakpoints passed during an incremental test: the intensity at which blood lactate begins to rise above baseline, and the highest intensity at which lactate production and elimination are in equilibrium.
That gives two anchors, commonly called LT1 and LT2. A marathon lasts far longer than the roughly one-hour effort usually associated with LT2, so the race has to be run somewhere below it.
What coaches and guides report
Two practical sources place marathon pace at the lower anchor. One running guide states that "LT1 sits at roughly marathon pace for trained runners", while LT2 is roughly the pace you could hold all-out for an hour, closer to half-marathon pace (Marathon Handbook). Coach Scott Johnston, describing paced track sessions with two ultrarunners in good racing form, reports lactate values "between 2-2.7 depending on the day, temps and wind" at marathon pace and argues the marathon "is competed at or a little above one's aerobic threshold" (Evoke Endurance forum).
Treat both as practitioner observations, not as a lab-validated rule for every runner.
What the older research shows
The classic study is Sjödin and Jacobs (1981, International Journal of Sports Medicine): in 18 Stockholm Marathon runners, the running velocity at a blood lactate of 4 mmol/L accounted for 92% of the variation in marathon velocity. Note what that says and what it does not. A strong correlation means runners with a faster 4 mmol/L velocity tended to run faster marathons; it does not mean they raced at 4 mmol/L. Coyle's 1995 review similarly describes early findings that marathon runners hold a velocity corresponding to the intensity at which lactate begins to accumulate in the blood.
One step test, four "threshold marathon paces"
The following is a fictional running step test, built to show how much the threshold definition moves a marathon projection. Treadmill, constant incline, one blood sample per stage.
| Speed (km/h) | 10 | 11 | 12 | 13 | 14 | 15 | 16 |
|---|---|---|---|---|---|---|---|
| Lactate (mmol/L) | 1.0 | 1.1 | 1.3 | 1.7 | 2.4 | 3.6 | 5.5 |
Interpolating linearly between stages and converting each speed into a marathon time (42.195 km at constant pace):
| Anchor | Speed | Pace per km | Marathon at that pace |
|---|---|---|---|
| LT1 (baseline + 0.5 = 1.5 mmol/L) | 12.50 km/h | 4:48 | 3:22:32 |
| 2.0 mmol/L | 13.43 km/h | 4:28 | 3:08:32 |
| 2.5 mmol/L | 14.08 km/h | 4:16 | 2:59:46 |
| Fixed 4.0 mmol/L | 15.21 km/h | 3:57 | 2:46:27 |
From the same blood samples, the projections span 36 minutes, from 2:46:27 to 3:22:32. Anyone told "run your marathon at lactate threshold pace" without a definition could be handed either end of that range.
Reading the example
The 4 mmol/L line is the one that misleads most in this data set: it projects a time that would require holding, for nearly three hours, an intensity the curve shows is already on its steep section. The LT1 line is the conservative end. The 2.0 to 2.5 mmol/L band, where the coach observations above cluster, lands between them.
None of these rows is a race plan. They show that a "threshold pace" figure is meaningless until you know which threshold, which method and which protocol produced it. Your own curve may sit very differently, and how to turn it into a race target is a decision for you and your coach.
Where runners go wrong with threshold-based marathon pace
Using the watch's "lactate threshold" as an LT2 lab value. Wearables estimate a threshold from heart rate and pace data. That estimate is its own metric. Comparing it with a blood-lactate LT1 from a step test mixes two definitions.
Projecting a marathon from a fixed 4 mmol/L value. As the fictional table shows, this anchor projected the fastest time by a wide margin. Use it only alongside a method that locates the first rise.
Ignoring conditions. Johnston's own range (2 to 2.7 mmol/L) already varies with day, temperature and wind. A step test on a cool treadmill in December and a race in warm spring weather are not the same conditions.
Comparing tests with different protocols. Stage length and step size change the shape of the curve. Keep the protocol fixed between tests, and note the method used for each threshold.
Testing over the winter build
Many spring marathon plans start their base phase in November or December, which makes this a natural point for a first step test and a later retest under the same conditions. What to record so the two results are comparable:
- Treadmill model and incline (or track and weather if outdoors)
- Stage length, step size, start speed
- Lactate meter and strip batch
- Which methods you read the result with, for example LT1 and LT2 side by side
LactateThreshold takes the stage data you enter and returns LT1, LT2, the lactate curve and training zones, so both anchors from the table above are visible in one analysis rather than collapsed into a single "threshold pace". The reasoning behind the zone boundaries is in Lactate threshold calculator: estimate LT1, LT2 and training zones, and the method differences in Calculate lactate threshold: methods and formulas explained.
If you have a heart condition or another health concern, clear a maximal step test with a physician before running one.
FAQ
Can a calculator turn my lactate threshold into a marathon pace?
A calculator can convert a threshold speed into a pace and a finish time, as the table above does. It cannot decide which threshold is the right anchor for you. In the fictional example, the same test gives projections from 2:46:27 to 3:22:32 depending on the definition, so the method choice matters more than the arithmetic.
Is a higher lactate threshold better?
For endurance performance, a threshold reached at a faster pace is generally associated with faster race times; Sjödin and Jacobs found the 4 mmol/L velocity explained 92% of the variation in marathon velocity in their 18 runners. That is a group-level correlation. Compare your own threshold over time using the same method rather than against other runners.
Is marathon pace the same as lactate threshold pace?
Usually not, if "lactate threshold" means LT2. Practitioner sources place trained runners' marathon pace close to LT1 or slightly above it, with LT2 nearer half-marathon pace. If your report gives a single "threshold pace", check which threshold it means before using it for a race.